Lambda-prophage induction modeled as a cooperative failure mode of lytic repression

We analyze a system-level model for lytic repression of lambda-phage in E. coli using reliability theory, showing that the repressor circuit comprises 4 redundant components whose failure mode is prophage induction. Our model reflects the specific biochemical mechanisms involved in regulation, including long-range cooperative binding, and its detailed predictions for prophage induction in E. coli under ultra-violet radiation are in good agreement with experimental data.Comment: added referenc

Coherent addition of two dimensional array of fiber lasers

Configurations for efficient free space coherent addition of four separate fiber lasers arranged in two dimensional array are presented. They include compact and robust interferometric combiners that can be inserted either inside or outside the cavity of the combined lasers system. The results reveal that over 85% combining efficiency can be obtained.Comment: To be published in Optics Communicatio

Evolutionary game theory in growing populations

Existing theoretical models of evolution focus on the relative fitness advantages of different mutants in a population while the dynamic behavior of the population size is mostly left unconsidered. We here present a generic stochastic model which combines the growth dynamics of the population and its internal evolution. Our model thereby accounts for the fact that both evolutionary and growth dynamics are based on individual reproduction events and hence are highly coupled and stochastic in nature. We exemplify our approach by studying the dilemma of cooperation in growing populations and show that genuinely stochastic events can ease the dilemma by leading to a transient but robust increase in cooperationComment: 4 pages, 2 figures and 2 pages supplementary informatio

Infection by <i>Salmonella enterica</i> Promotes or Demotes Tumor Development

Cancer is a disease that claims the lives of millions of people every year around the world. To date, multiple risk factors that may contribute to its development have been described. In recent years, a factor that has been associated to cancer development is the presence of bacterial infections that could contribute to its occurrence not only by favoring the inflammatory process, but also through the release of proteins that trigger tumorigenesis. One of the bacterial species that have recently generated interest due to its possible role in cancer development is Salmonella enterica. Nevertheless, for more than a decade, attenuated strains of Salmonella enterica have been proposed as a treatment for different neoplasms due to its bacterium tropism for the tumor microenvironment, its oncolytic activity and its ability to activate the innate and adaptive immune responses of the host. These two facets of Salmonella enterica are addressed in detail in this chapter, allowing us to understand its possible role in cancer development and its well-documented antitumor activity

Assembly and use of new task rules in fronto-parietal cortex

Severe capacity limits, closely associated with fluid intelligence, arise in learning and use of new task rules. We used fMRI to investigate these limits in a series of multirule tasks involving different stimuli, rules, and response keys. Data were analyzed both during presentation of instructions and during later task execution. Between tasks, we manipulated the number of rules specified in task instructions, and within tasks, we manipulated the number of rules operative in each trial block. Replicating previous results, rule failures were strongly predicted by fluid intelligence and increased with the number of operative rules. In fMRI data, analyses of the instruction period showed that the bilateral inferior frontal sulcus, intraparietal sulcus, and presupplementary motor area were phasically active with presentation of each new rule. In a broader range of frontal and parietal regions, baseline activity gradually increased as successive rules were instructed. During task performance, we observed contrasting fronto-parietal patterns of sustained (block-related) and transient (trial-related) activity. Block, but not trial, activity showed effects of task complexity. We suggest that, as a new task is learned, a fronto-parietal representation of relevant rules and facts is assembled for future control of behavior. Capacity limits in learning and executing new rules, and their association with fluid intelligence, may be mediated by this load-sensitive fronto-parietal network

Apical Ballooning Syndrome: A Complication of Dual Chamber Pacemaker Implantation

Apical ballooning is a cardiac syndrome (Takotsubo Cardiomyopathy) described as a typical form of acute transient left ventricular dysfunction. While its onset has often been associated with emotionally or physically stressful situations, it has an overall favorable prognosis. We describe here a case of transient apical ballooning following permanent pacemaker implantation

Measurement-based modeling of bromine chemistry at the Dead Sea boundary layer ? Part 2: The influence of NO₂ on bromine chemistry at mid-latitude areas

International audienceUnderstanding the interaction between anthropogenic air pollution and Reactive Halogen Species (RHS) activity has had only limited support of direct field measurements, due to the fact that past field measurements of RHS have been mainly performed in Polar Regions. The present paper investigates the interaction between NO2 and Reactive Bromine Species (RBS) activity by model simulations based on extensive field measurements performed in the Dead Sea area, as described in a companion paper (Tas et al., 2006). The Dead Sea is an excellent natural laboratory for this investigation since elevated concentrations of BrO (up to more than 150 pptv) are frequently observed, while the average levels of NO2 are around several ppb. The results of the present study show that under the chemical mechanisms that occur at the Dead Sea, higher levels of NO2 lead to higher daily average concentrations of BrOX, as a result of an increase in the rate of the heterogeneous decomposition of BrONO2 that in turn causes an increase in the rate of the "Bromine Explosion" mechanism. The present study has shown that the influence of NO2 on BrOX production clearly reflects an enhancement of RBS activity caused by anthropogenic activity. However, above a certain threshold level of NO2 (daily average mixing ratios of 0.2 ppbv during RBS activity), the daily average concentrations of BrOX decrease for a further increase in the NO2 concentrations

Observation of Quantum Effects in sub Kelvin Cold Reactions

There has been a long-standing quest to observe chemical reactions at low temperatures where reaction rates and pathways are governed by quantum mechanical effects. So far this field of Quantum Chemistry has been dominated by theory. The difficulty has been to realize in the laboratory low enough collisional velocities between neutral reactants, so that the quantum wave nature could be observed. We report here the first realization of merged neutral supersonic beams, and the observation of clear quantum effects in the resulting reactions. We observe orbiting resonances in the Penning ionization reaction of argon and molecular hydrogen with metastable helium leading to a sharp increase in the absolute reaction rate in the energy range corresponding to a few degrees kelvin down to 10 mK. Our method is widely applicable to many canonical chemical reactions, and will enable a breakthrough in the experimental study of Quantum Chemistry